<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script type="text/javascript" src="../js/vue.js"></script>
</head>
<body>
<!--
				监视属性watch：
					1.当被监视的属性变化时, 回调函数自动调用, 进行相关操作
					2.监视的属性必须存在，才能进行监视！！
					3.监视的两种写法：
							(1).new Vue时传入watch配置
							(2).通过vm.$watch监视
		 -->
<div id="root">
    <h2>今天天气很{{weatherInfo}}</h2>
    <button @click="changeWeather">切换天气</button>
    <hr>
    <h3>a的值是：{{numbers.a}}</h3>
    <button @click="numbers.a++">点击让a+1</button>
    <h3>b的值是：{{numbers.b}}</h3>
    <button @click="numbers.b++">点击让b+1</button>
</div>
</body>
<script type="text/javascript">
    Vue.config.productionTip = false;
    const vm = new Vue({
        el: '#root',
        data() {

            return {
                isHot: true,
                numbers: {
                    a: 1,
                    b: 2
                }
            }
        },
        methods: {
            changeWeather(e) {
                this.isHot = !this.isHot;
            }
        },
        computed: {
            weatherInfo: {
                get() {
                    return (this.isHot ? "炎热" : "凉爽");
                }
            }
        },
        watch: {
            isHot: {
                // immediate: true, // 初始化时调用一下handler
                handler(valNew, valOld) {
                    console.log("isHot changed", valNew, valOld);
                }
            },
            /*'numbers.a': {
                immediate: false,
                handler(valNew, valOld){
                    console.log('a changed');
                }
            },
            'numbers.b': {
                immediate: false,
                handler(valNew, valOld){
                    console.log('b changed');
                }
            },*/
            'numbers': {
                immediate: false,
                deep:true,
                handler(valNew, valOld){
                    console.log('numbers changed');
                }
            }
        }
    });
</script>
</html>